Yeah, the 1690 is a flaky bit of i'm afraid. I just turned mine on .. it ... sat ..... there .... sulking ...... forever saying 'Loading Maps'. So i forced it off. Sticking on loading maps like that is usually a sign that the unit is bricked. But not the mighty 1690, it just has a mind of it's own. Next press of the on button and it happily booted up.

Try clearing NV. Go to Map screen, press 'Speed' > press and hold the Speedometer for ~6 seconds > Developer Info > Nonvol Available > Clear Nonvol > Yes. A little more comprehensive than a hard reset so worth a try. Or throw it at a wall, either is good ...... ['cos it's just a piece of cr*p!]

PS: Don't actually throw it at a wall, wall damage may result.